Variable frequency excitation plasma device for thermal and non-thermal tissue effects

ABSTRACT

A plasma system is disclosed. The plasma system includes a plasma instrument having an elongated body defining a lumen therethrough and a first electrode and a second electrode; an ionizable media source in fluid communication with the lumen and configured to supply ionizable media thereto; and a variable frequency energy source adapted to be coupled to the first and second electrodes and configured to supply energy to the first and second electrodes sufficient to ignite ionizable media supplied by the ionizable media source to generate a plasma influent, wherein a frequency of the energy is adjustable to modify at least one property of the plasma effluent.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 14/549,022, filed on Nov. 20, 2014, now U.S. Pat. No.10,237,962, which claims the benefit of and priority to U.S. ProvisionalPatent Application No. 61/945,000, filed Feb. 26, 2014, the entirecontents of which are incorporated by reference herein.

BACKGROUND Technical Field

The present disclosure relates to plasma devices and processes forsurface processing and tissue treatment. More particularly, thedisclosure relates to a bipolar coagulation handpiece for generatingchemically reactive, plasma-generated species.

Background of Related Art

Electrical discharges in dense media, such as liquids and gases at ornear atmospheric pressure, can, under appropriate conditions, result inplasma formation. Plasmas have the unique ability to create largeamounts of chemical species, such as ions, radicals, electrons,excited-state (e.g., metastable) species, molecular fragments, photons,and the like. The plasma species may be generated in a variety ofinternal energy states or external kinetic energy distributions bytailoring plasma electron temperature and electron density. In addition,adjusting spatial, temporal and temperature properties of the plasmacreates specific changes to the material being irradiated by the plasmaspecies and associated photon fluxes. Plasmas are also capable ofgenerating photons including energetic ultraviolet photons that havesufficient energy to initiate photochemical and photocatalytic reactionpaths in biological and other materials that are irradiated by theplasma photons. There is a need for plasma devices that are configuredfor providing various tissue effects by varying above-describedproperties of the plasma.

SUMMARY

Plasmas have broad applicability and provide alternative solutions toindustrial, scientific and medical needs, especially workpiece (e.g.,tissue) surface treatment at any temperature range. Plasmas may bedelivered to the workpiece, thereby affecting multiple changes in theproperties of materials upon which the plasmas impinge. Plasmas have theunique ability to create large fluxes of radiation (e.g., ultraviolet),ions, photons, electrons and other excited-state (e.g., metastable)species which are suitable for performing material property changes withhigh spatial, material selectivity, and temporal control. Plasmas mayalso remove a distinct upper layer of a workpiece with little or noeffect on a separate underlayer of the workpiece or it may be used toselectively remove a particular tissue from a mixed tissue region orselectively remove a tissue with minimal effect to adjacent organs ofdifferent tissue type.

The plasma species are capable of modifying the chemical nature oftissue surfaces by breaking chemical bonds, substituting or replacingsurface-terminating species (e.g., surface functionalization) throughvolatilization, gasification or dissolution of surface materials (e.g.,etching). With proper techniques, material choices and conditions, it ispossible to remove one type of tissue entirely without affecting anearby different type of tissue. Controlling plasma conditions andparameters (including S-parameters, V, I, Θ, and the like) allows forthe selection of a set of specific particles, which, in turn, allows forselection of chemical pathways for material removal or modification aswell as selectivity of removal of desired tissue type.

According to one embodiment of the present disclosure, a plasma systemis disclosed. The plasma system includes a plasma instrument having anelongated body defining a lumen therethrough and a first electrode and asecond electrode; an ionizable media source in fluid communication withthe lumen and configured to supply ionizable media thereto; and avariable frequency energy source adapted to be coupled to the first andsecond electrodes and configured to supply energy to the first andsecond electrodes sufficient to ignite ionizable media supplied by theionizable media source to generate a plasma influent, wherein afrequency of the energy is adjustable to modify at least one property ofthe plasma effluent.

According to one aspect of the above embodiment, at least one of thevariable frequency energy source or the plasma instrument includescontrols for adjusting the frequency.

According to another aspect of the above embodiment, the ionizable mediasource is adapted to be coupled to the variable frequency energy source.

According to a further aspect of the above embodiment, wherein thevariable frequency energy source is configured to adjust the frequencybased on a flow rate of the ionizable media from the ionizable mediasource. The plasma instrument may include an applicator tip coupled to adistal end of the elongated body. The applicator tip may also define asecond lumen in fluid communication with the lumen of the elongatedbody. The first electrode may be disposed on an outer surface of theapplicator tip. The second electrode may be disposed within at least oneof the lumen of the elongated body or the second lumen.

According to one aspect of the above embodiment, the frequency isadjustable to a first frequency at which the plasma effluent is at afirst temperature and a second frequency higher than the first frequencyat which the plasma effluent is at a second temperature higher than thefirst temperature.

According to another aspect of the above embodiment, the energy sourceincludes: a non-resonant radio frequency output stage configured tooutput an excitation waveform; and a controller coupled to thenon-resonant radio frequency output stage, the controller configured toadjust the frequency of the excitation waveform on a cycle-by-cyclebasis. The non-resonant radio frequency output stage includes: a DC-DCbuck converter configured to output a DC waveform, the DC-DC buckconverter including at least one first switching element operated at afirst duty cycle. The non-resonant radio frequency output stage furtherincludes: a DC-AC boost converter coupled to the DC-DC buck converterand including at least one second switching element operated at a secondduty cycle, the DC-AC boost converter configured to convert the DCwaveform to generate the excitation waveform. The controller is coupledto the DC-DC buck converter and the DC-AC boost converter and thecontroller is further configured to adjust the second duty cycle toadjust the duty cycle of the excitation waveform.

According to another embodiment of the present disclosure, a method isdisclosed. The method includes: supplying ionizable media from anionizable media source to a plasma instrument, the plasma instrumentincluding an elongated body defining a lumen therethrough and first andsecond electrodes; supplying an excitation waveform from a variablefrequency energy source to the first and second electrodes to igniteionizable media supplied by the ionizable media source and to generate aplasma influent; and adjusting a frequency of the excitation waveform tomodify at least one property of the plasma effluent.

According to one aspect of the above embodiment, adjustment of thefrequency includes adjustment a variable setting element disposed on theplasma instrument. Adjustment of the frequency includes inputting adesired frequency using a frequency user interface of the variablefrequency energy source. Adjustment of the frequency includes inputtingthe frequency based on a flow rate of the ionizable media from theionizable media source. Adjustment of the frequency includes setting toat least one of a first frequency at which the plasma effluent is at afirst temperature and a second frequency higher than the first frequencyat which the plasma effluent is at a second temperature higher than thefirst temperature.

According to one aspect of the above embodiment, supplying theexcitation waveform includes operating at least one switching element ofa DC-AC boost converter at a duty cycle to convert a DC waveform togenerate the excitation waveform. Adjustment of the frequency includesadjustment the duty cycle.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate exemplary embodiments of thedisclosure and, together with a general description of the disclosuregiven above, and the detailed description of the embodiments givenbelow, serve to explain the principles of the disclosure, wherein:

FIG. 1 is a perspective view of a plasma system according to the presentdisclosure;

FIG. 2 is a front elevational view of one embodiment of anelectrosurgical generator according to the present disclosure;

FIG. 3 is a schematic, block diagram of the embodiment of theelectrosurgical generator of FIG. 2 according to the present disclosure;

FIG. 4 is a schematic, block diagram of a DC-DC converter and a DC-ACinverter of the electrosurgical generator of FIG. 2 according to thepresent disclosure;

FIG. 5 is a longitudinal cross-sectional, side view of the plasmainstrument of the embodiment of FIG. 1 according to the presentdisclosure; and

FIG. 6 is a partial cross-sectional, perspective view of the enlargedarea 6 as indicated in FIG. 5 of an elongated body of the plasmainstrument embodiment of FIG. 1 according to the present disclosure.

DETAILED DESCRIPTION

Embodiments of the presently disclosed electrosurgical system, apparatusand/or device are described in detail with reference to the drawings, inwhich like reference numerals designate identical or correspondingelements in each of the several views. As used herein the term “distal”refers to that portion of the electrosurgical system, apparatus and/ordevice, or component thereof, that are farther from the user, while theterm “proximal” refers to that portion of the electrosurgical system,apparatus and/or device, or component thereof, that are closer to theuser.

In general, referring to FIG. 1, the present disclosure provides anelectrosurgical plasma system 10 including a source of ionizable media16 and an electrosurgical generator 200 configured to output energy at avariable frequency. The plasma system 10 also includes a plasmainstruments 12 adapted to be coupled to the source of ionizable media 16and to the electrosurgical generator 200. The plasma instrument 12and/or the generator 200 include controls for adjusting the frequency ofthe electrosurgical generator 200, which in turn, adjusts one or moreproperties (e.g., temperature) of a plasma effluent generated by theplasma instrument 12. This allows for tailoring of the plasma effluentto achieve desired tissue effects. In embodiments, frequency may beadjusted in response to automated input (e.g., by the generator 200 inresponse to detected tissue and/or energy properties, ionizable mediaflow, and combinations thereof) and/or user input (e.g., selecting oneor more operational mode).

Plasmas according to the present disclosure may be used to coagulate,cauterize, or otherwise treat tissue through direct application ofhigh-energy plasma. In particular, kinetic energy transfer from theplasma to the tissue causes healing, and thus, affects thermalcoagulation of bleeding tissue. In embodiments, plasma beam coagulationmay be accomplished using a handheld electrosurgical instrument havingone or more electrodes energizable by an electrosurgical generator,which outputs a high-intensity electric field suitable for formingplasma using ionizable media (e.g., inert gas).

The plasma system 10 according to the present disclosure is capable ofgenerating plasmas having a temperature from about 60° C. to about 300°C. (“high temperature plasmas”), in embodiments from about 20° C. toabout 60° C. (“low temperature plasmas”). These temperatures for lowtemperature plasmas represent average temperatures since the particlesare not in thermal equilibrium so some particles may have relativelyhigh temperatures, however, these high temperature particles are a smallportion of the plasma, so the average plasma temperature is low.

The high-temperature plasmas cause thermal effects upon tissue bydelivering a stream of high-temperature ionized argon gas through anelectric arc. Effects of these instruments are purely thermal and aresimilar to tissue effects obtained using a handheld butane torch, whichalso emits plasma, in the form of fire. These types of plasmas arewell-suited for coagulating, cutting, vaporizing or otherwise treatingtissue.

The low-temperature plasmas may be generated using corona discharges andaffect tissue through non-thermal mechanisms. Plasmas produced throughcorona discharge ionize a small portion of the ionizable media (e.g.,feedstock gas), causing the plasma to have a low average temperature.These low-temperature plasma discharges affect tissue throughelectroporation and production of reactive species. These types ofplasmas are also well-suited for wound sterilization, drug delivery,wound closure, and other medical and surgical procedures. Inembodiments, low-temperature plasma may be used for application ofvarious bioactive agents

Plasmas according to the present disclosure may be produced by DC or ACpulses. Low-temperature plasmas may be produced by applying low DC or ACpulses to the electrodes of the instrument at low duty cycles. Whilehigh-temperature plasmas may be produced by applying high frequency DCor AC pulses at high duty cycles. In embodiments, the impedance of theinstrument (e.g., electrodes and other electrically-coupling components)may be entirely capacitive, thus, increasing frequencies encounter lowerimpedance in the instrument, allowing more power to be applied to theionization process. A greater degree of ionization also increases theplasma temperature. Varying the gas flow rate, pulse width, andrepetition rate may also be used to adjust the amount of ionization.

The plasma system 10 according to the present disclosure provides forgeneration of both non-thermal and thermal plasmas. The generator 200 ofthe presently disclosed plasma system 10 allows for adjustment of thefrequency of the plasma excitation waveform. The generator 200 combinesthese features into a single apparatus, which improves utility of bothtechnologies (e.g., thermal and non-thermal plasmas) and allows forseamless transition between both applications.

Plasmas according to the present disclosure may be generated usingelectrical energy that is delivered as either direct current (DC)electricity or alternating current (AC) electricity at frequencies fromabout 0.1 hertz (Hz) to about 100 gigahertz (GHz), including radiofrequency (“RF”, from about 0.1 MHz to about 100 MHz) and microwave(“MW”, from about 0.1 GHz to about 100 GHz) bands, using appropriategenerators, electrodes, and/or antennas. In embodiments, variousproperties of the plasma according to the present disclosure may bemodified by adjusting excitation frequency, operating voltage, current,levels, phase, electron temperature and density, and combinationsthereof.

With continued reference to FIG. 1, a plasma system 10 will now bedescribed in detail. The system 10 includes a plasma instrument 12 thatis coupled to a generator 200, an ionizable media source 16 which mayalso include an optional precursor source (not shown). The generator 200includes any suitable components for delivering power to the plasmainstrument 12. The generator 200 may be any radio frequency generator orother suitable power source capable of producing power to ignite theionizable media to generate plasma. In embodiments, electrosurgicalenergy is supplied to the instrument 12 by the generator 200 through aninstrument cable 4. The cable 4 includes a supply lead 4 a connectingthe plasma instrument 12 to an active terminal 230 (FIG. 3) of thegenerator 200 and a return lead connecting the instrument 12 to a returnterminal 232 (FIG. 3) of the generator 200. The plasma instrument 12 maybe utilized as an electrosurgical pencil for application of plasma totissue. The generator 200 may be an electrosurgical generator that isadapted to supply the instrument 12 with electrical power at a frequencyfrom about 100 kHz to about 4 MHz, in embodiments the frequency may befrom about 200 kHz to about 3 MHz, in further embodiments the frequencymay be from about 300 kHz to about 1 MHz.

With reference to FIG. 2, a front face 240 of the generator 200 isshown. The generator 200 may be of any suitable type (e.g.,electrosurgical, microwave, etc.) and may include a plurality ofconnectors 250-262 to accommodate various types of electrosurgicalinstruments (e.g., electrosurgical forceps, electrosurgical pencils,ablation probes, etc.) in addition to the plasma instrument 12 as shownin FIGS. 1, 5, and 6.

The generator 200 includes a user interface 241 having one or moredisplay screens 242, 244, 246 for providing the user with variety ofoutput information (e.g., frequency setting, intensity settings,treatment complete indicators, etc.). Each of the screens 242, 244, 246is associated with corresponding connector 250, 252, 254, 256, 258, 260,and 262. The generator 200 includes suitable input controls (e.g.,buttons, activators, switches, touch screen, etc.) for controlling thegenerator 200. The display screens 242, 244, 246 are also configured astouch screens that display a corresponding menu for the electrosurgicalinstruments (e.g., plasma instrument 12, etc.). The user then adjustsinputs by simply touching corresponding menu options.

Screen 242 controls monopolar output and the devices connected to theconnectors 250 and 252. Connector 250 is configured to couple to amonopolar electrosurgical instrument (e.g., electrosurgical pencil) andconnector 252 is configured to couple to a foot switch (not shown). Thefoot switch provides for additional inputs (e.g., replicating inputs ofthe generator 200). Screen 244 controls monopolar, plasma and bipolaroutput and the devices connected to the connectors 256 and 258.Connector 256 is configured to couple to other monopolar instruments.Connector 258 is configured to couple to plasma instrument 12. Connector254 may be used to connect to one or more return electrode pads (notshown). Screen 246 controls plasma procedures performed by the plasmainstrument 12 that may be plugged into the connectors 260 and 262.

FIG. 3 shows a schematic block diagram of the generator 200 configuredto output electrosurgical energy. The generator 200 includes acontroller 224, a power supply 227, and a radio-frequency (RF) amplifier228. The power supply 227 may be a high voltage, DC power supplyconnected to an AC source (e.g., line voltage) and provides highvoltage, DC power to the RF amplifier 228 via leads 227 a and 227 b,which then converts high voltage, DC power into treatment energy (e.g.,electrosurgical or microwave) and delivers the energy to the activeterminal 230. The energy is returned thereto via the return terminal232. The active and return terminals 230 and 232 and coupled to the RFamplifier 228 through an isolation transformer 229. The RF amplifier 228is configured to operate in a plurality of modes, during which thegenerator 200 outputs corresponding waveforms having specific dutycycles, peak voltages, crest factors, etc. It is envisioned that inother embodiments, the generator 200 may be based on other types ofsuitable power supply topologies.

The controller 224 includes a processor 225 operably connected to amemory 226, which may include transitory type memory (e.g., RAM) and/ornon-transitory type memory (e.g., flash media, disk media, etc.). Theprocessor 225 includes an output port that is operably connected to thepower supply 227 and/or RF amplifier 228 allowing the processor 225 tocontrol the output of the generator 200 according to either open and/orclosed control loop schemes. A closed loop control scheme is a feedbackcontrol loop, in which a plurality of sensors measure a variety oftissue and energy properties (e.g., tissue impedance, tissuetemperature, output power, current and/or voltage, etc.), and providefeedback to the controller 224. The controller 224 then signals thepower supply 227 and/or RF amplifier 228, which adjusts the DC and/orpower supply, respectively. Those skilled in the art will appreciatethat the processor 225 may be substituted for by using any logicprocessor (e.g., control circuit) adapted to perform the calculationsand/or set of instructions described herein including, but not limitedto, field programmable gate array, digital signal processor, andcombinations thereof.

The generator 200 according to the present disclosure includes aplurality of sensors 280, e.g., an RF current sensor 280 a, and an RFvoltage sensor 280 b. Various components of the generator 200, namely,the RF amplifier 228, the RF current and voltage sensors 280 a and 280b, may be disposed on a printed circuit board (PCB). The RF currentsensor 280 a is coupled to the active terminal 230 and providesmeasurements of the RF current supplied by the RF amplifier 228. The RFvoltage sensor 280 b is coupled to the active and return terminals 230and 232 provides measurements of the RF voltage supplied by the RFamplifier 228. In embodiments, the RF current and voltage sensors 280 aand 280 b may be coupled to active and return leads 228 a and 228 b,which interconnect the active and return terminals 230 and 232 to the RFamplifier 228, respectively.

The RF current and voltage sensors 280 a and 280 b provide the sensed RFvoltage and current signals, respectively, to the controller 224, whichthen may adjust output of the power supply 227 and/or the RF amplifier228 in response to the sensed RF voltage and current signals. Thecontroller 224 also receives input signals from the input controls ofthe generator 200, the instrument 20 and/or forceps 30. The controller224 utilizes the input signals to adjust power outputted by thegenerator 200 and/or performs other control functions thereon.

FIG. 4 shows another embodiment of the generator 200 configured tooperate with near-deadbeat control to maintain a desired AC output ofgenerator 200. As used herein, the terms “deadbeat” or “near-deadbeat”refer to adjustments being made by the generator 200 to the output fromabout 1 cycle of the waveform to about 100 cycles, in embodiments fromabout 10 cycles to about 25 cycles. The term cycle refers to a fullcycle of a waveform (e.g., excitation waveform for igniting ionizablemedia) having a positive and negative half cycle. The generator 200according to the present disclosure may have an operating frequency offrom about 100 kHz to about 4,000 kHz, and in embodiments, from about200 kHz to about 3,000 kHz, in further embodiments the frequency mayrange from about 300 kHz to about 1 MHz, thus, the generator 200operating at the predetermined frequency of 100 kHz outputs a waveformhaving 100,000 cycles per second.

The adjustments to the output can be made at the same frequency (e.g., 1cycle of the electrosurgical waveform) or a factor of about 0.1 (e.g.,every 10 cycles of the electrosurgical waveform). In accordance with anexemplary embodiment, near-deadbeat control ensures that only a desiredquantum of power is delivered to the electrosurgical instrument. In theprior art generators, slow transient response of the converter tochanges in load impedance may result in excessive delivery of power thatmay not be detected for 500 cycles or more.

The generator 200 is also configured to operate in any of a constantvoltage limit mode, a constant current limit mode, a constant powermode, and combinations thereof. The mode selection is generally based onthe impedance associated with the load, e.g., gas flow.

With respect to the AC output of the generator 200 and in exemplaryembodiments, “constant power” is defined to mean the average powerdelivered in each switching cycle is substantially constant. Likewise,“constant voltage” and “constant current” are defined as modes where theroot mean square (RMS) value of the AC voltage or current, respectively,is regulated to a substantially fixed value.

With reference to the schematic shown in FIG. 4, the generator 200includes a DC-DC buck converter 101, a DC-AC boost converter 102, aninductor 103, a transformer 104, and the controller 224. In embodiments,the DC-DC buck converter 101 and the DC-AC boost converter 102 are partof the RF output stage 228. In the exemplary embodiment, a DC voltagesource Vg, such as the power supply 227, is connected to DC-DC buckconverter 101. Furthermore, inductor 103 is electrically coupled betweenDC-DC buck converter 101 and DC-AC boost converter 102. The output ofDC-AC boost converter 102 transmits power to the primary winding oftransformer 104, which passes through the secondary winding oftransformer 104 to the load Z (e.g., ionizable media).

The DC-DC buck converter 101 includes a switching element 101 a and theDC-AC boost converter 102 includes a plurality of switching elements 102a-102 d arranged in an H-bridge topology. In embodiments, the DC-ACboost converter 102 may be configured according to any suitable topologyincluding, but not limited to, half-bridge, full-bridge, push-pull, andthe like. Suitable switching elements include voltage-controlled devicessuch as transistors, field-effect transistors (FETs), combinationsthereof, and the like. In an exemplary embodiment, controller 224 is incommunication with both DC-DC buck converter 101 and DC-AC boostconverter 102, in particular, the switching elements 101 a and 102 a-102d, respectively. The controller 224 is configured to output controlsignals, which may be a pulse-width modulated signal, to the switchingelements 101 a and 102 a-102 d as described in further detail below withrespect to the voltage-mode controller 112. The controller 224 isconfigured to control the duty cycle d1 of the control signal suppliedto the switching element 101 a of the DC-DC buck converter 101 and theduty cycle d2 of the control signals supplied to the switching elements102 a-102 d of the DC-AC boost converter 102. Additionally, controller224 is configured to measure power characteristics of generator 200, andcontrol generator 200 based at least in part on the measured powercharacteristics. Examples of the measured power characteristics include,but are not limited to, the current through inductor 103 and the voltageat the output of DC-AC boost converter 102. In an exemplary embodiment,controller 224 controls buck converter 101 by generating the duty cycled1 based on a comparison of the inductor current and a nonlinear carriercontrol current for every cycle.

In accordance with an exemplary embodiment, controller 224 may include acurrent-mode controller 111, a voltage-mode controller 112, a modeselector 113, and steering logic 114. The mode selector 113 compares theoutput voltage V_(out)(t) and the inductor current i_(L)(t) to setlimits in order to determine the desired mode of operation of thegenerator 200. The operational mode may be of constant (or maximum)current Imax, constant power P₁ from DC-DC buck converter 101, constantpower P₂ from DC-AC boost converter 102, or constant (or maximum)voltage V_(max), or combinations thereof. The output selection of modeselector 113 is communicated to steering logic 114. In an exemplaryembodiment, steering logic 114 controls which of at least one ofcurrent-mode controller 111 and voltage mode controller 112 are enabled.Furthermore, steering logic 114 selects which conversion stage receivesthe output of current-mode controller 111 and/or voltage-mode controller112.

In one exemplary embodiment, steering logic 114 switches betweenoperating either DC-DC buck converter 101 or DC-AC boost converter 102with current-mode control for constant power, depending on which portionof the desired output characteristics is being produced. The voltagemode controller 112 and/or current mode controller 111 adjust the dutycycles d1 and/or d2 for current mode control. Furthermore, steeringlogic 114 selects the duty cycle that each of DC-DC buck converter 101and/or DC-AC boost converter 102 receives.

The current-mode controller 111 compares the inductor current i_(L)(t)to nonlinear carrier control current i_(C)(t) (e.g., desired set pointcurrent). In an exemplary embodiment, the nonlinear carrier controlcurrent i_(C) is set by the selection of Pset (e.g., desired power setpoint), which may be done by a user, or provided by a lookup table. Inan exemplary embodiment, current-mode controller 111 uses a latchcircuit to compare inductor current i_(L)(t) to either a current limitsignal (I) or a power limit signal (P₁). The control signal for thelatch circuit is the mode signal, which is communicated from steeringlogic 114. The inputs of the latch circuit are a clock signal and eitherthe current limit signal (I) or a power limit signal (P₁). The selectionof the current-mode controller 111 output is in response to the currentmode of the generator 200. The operating mode of the generator 200 maybe communicated by the mode selector 113. In an exemplary embodiment,the switching waveform d(t) is switched “high” at the start of aswitching period if the inductor current i_(L)(t) is lower thannonlinear carrier control current i_(C)(t). Furthermore, in theexemplary embodiment, the switching waveform d(t) is switched “low” inresponse to the inductor current i_(L)(t) exceeding the nonlinearcarrier control current i_(C)(t). In other words, a comparison of theinductor current i_(L)(t) to nonlinear carrier control current i_(C)(t)facilitates adjusting pulse duration of duty cycle d1 of the buckconverter 101, as previously described.

To generate and control a constant current from generator 200, theaverage value of inductor current i_(L)(t) is set to be substantiallyequal to fixed control current limit K*Pset. For small inductor currentripple, in other words Δi_(L)<<I_(L), the current-mode controllerregulates the inductor current i_(L)(t) to an approximately constantvalue, which is substantially equal to the fixed control current limit.In accordance with an exemplary embodiment, the current-mode controller111 is able to maintain an approximately constant value of inductorcurrent i_(L)(t) by adjusting the current within from about 1 cycle toabout 100 cycles, in embodiments from about 2 to about 20 cycles, infurther embodiments, from about 3 to about 10 cycles. This low cycleadjustment provides for near-deadbeat or deadbeat control as describedabove.

In an exemplary embodiment and with continued reference to FIG. 4,voltage-mode controller 112 of the controller 224 includes a comparator121, a compensator 122, and a pulse-width modulator (PWM) 123. In anexemplary embodiment, voltage-mode controller 112 compares the outputvoltage V_(out)(t) with a reference voltage V_(max) at comparator 121.The output of comparator 121 is communicated to compensator 122, whichin turn, outputs an error signal that drives PWM 123. In the exemplaryembodiment, the output of compensator 122 is passed through PWM 123,which sets the duty cycle d2 of the signal in certain modes.

With respect to constant power output mode, constant AC power output isachieved by setting one or both of duty cycle d1 and duty cycle d2 todesired values. In various embodiments, the converter switches of thesteering logic 114 between generating constant power using DC-DC buckconverter 101 or DC-AC boost converter 102, depending on the impedanceof the load. Moreover, in various embodiments, generator 200 may operateboth DC-DC buck converter 101 and/or DC-AC boost converter 102 at thesame time, which results in a constant power output having a highvoltage and low power.

In steady-state and operating at a first constant power level, inductorcurrent i_(L)(t) is compared to a nonlinear carrier control currenti_(C)(t) in current-mode controller 111. The pulse duration of the dutycycle d1 of the DC-DC buck converter is varied using the current modecontroller 111. The varying pulse duration of the duty cycle controlsthe inductor current i_(L)(t), which is responsive to the load incontact with the buck converter. As the impedance of the load varies,the voltage across and the current through the inductor 103 also vary.As previously described, at the beginning of the duty cycle, the activeportion of the duty cycle is initiated. In response to the inductorfeedback signal exceeding the nonlinear carrier control current, theduty cycle switches to the non-active portion. The duty cycle stays inthe non-active portion until the end of the duty cycle, upon which thenext duty cycle begins in the active portion. In alternativeembodiments, during the comparison of the inductor feedback signal andthe nonlinear carrier control current, once the control current exceedsthe inductor current, the duty cycle switches to the active portion. Inaccordance with the exemplary embodiment, generator 200 generatesconstant power using DC-DC buck converter 101.

In steady-state and operating at a second constant power level, theaverage voltage of V₁(t) is constant in response to the input voltage Vgbeing constant, the DC-DC buck converter 101 is also disabled, sincethere is no voltage across inductor 103. The use of current programmedmode control results in the average current of i_(L)(t) being regulatedto an approximately fixed value with deadbeat or near-deadbeat control.In order to regulate i_(L)(t), duty cycle d2 is varied by the currentmode controller to maintain i_(L)(t) at a fixed value. Given the fixedvoltage and current, the power at input of DC-AC boost converter 102 isalso constant. In an exemplary embodiment, the DC-AC boost converter 102is nearly lossless, resulting in the output power being approximatelyequal to the input power. Since the input power is constant, the outputpower of DC-AC boost converter 102 is also constant.

With respect to constant voltage output mode, constant voltage output isachieved by setting duty cycle d1 of DC-DC buck converter 101 to a fixedvalue, and duty cycle d2 of DC-AC boost converter 102 is voltage-modecontrolled. In an exemplary embodiment, the voltage-mode controlinvolves measuring the output voltage of DC-AC boost converter 102 witha sensor network, feeding the sensed output voltage to a control loop involtage-mode controller 112, and adjusting the converter's duty cyclecommand based on the relative difference between the measured outputvoltage and the reference output voltage. In other words, the duty cycled2 is set to increase or decrease the output voltage to match V_(limit).In an exemplary embodiment, V_(limit) may be set by a user or based onvalues in a look-up table. In an alternative embodiment, the boostinverter is run at a fixed duty cycle with no feedback of the outputvoltage.

With respect to constant current output mode, constant current output isachieved by operating DC-AC boost converter 102 at a fixed duty cycle d2and current-mode controlling DC-DC buck converter 101. In an exemplaryembodiment, the current-mode control accurately controls the averageinductor current such that the output of buck converter 101 is aconstant current. In one constant current embodiment, current-modecontroller 111 compares inductor current i_(L)(t) to a constant currenti_(c), which is set by K*Pset, where K*Pset is a constant current set bythe user during use. In various embodiments, Pset is set during thedesign stage.

In other words, controller 224 is configured to vary duty cycle d1 inorder to maintain inductor current i_(L)(t) at the fixed value. As aresult, the constant current output mode produces an AC output currentwhose magnitude is regulated with near-deadbeat speed. In an exemplaryembodiment, the generator 200 implementing the three modes of constantpower, constant voltage, or constant current produces a very fast, veryaccurate regulation of the AC output characteristic. Various modes areimpacted by monitored characteristics, while other modes do not need torespond to the same monitored characteristics. Specifically, controller224 may switch between operating modes based in part on monitoredcharacteristics, such as inductor current and voltage. In other words,the selection of which stage of the converter to current-mode control isachieved with minimal feedback and without a need for extraneousmeasurements, averaging, or feedback of the output. Also, and aspreviously mentioned, the controller 224 performs near deadbeat controlby regulating inductor current to an approximately constant value, equalto a reference current.

Transitioning between the three modes, in an exemplary embodiment, isdetermined by monitoring the voltage of the primary winding oftransformer 104 and the inductor current. Furthermore, the determinationof transitioning between the modes is also based on the voltage andcurrent of inductor 103. The controller 224 transitions modes fromconstant current to constant power to constant voltage as the outputvoltage increases. Specifically, in an exemplary embodiment, thegenerator 200 operates in the constant current mode if the outputvoltage is less than a first voltage limit (V_(limit_1)). If the outputvoltage exceeds the first voltage limit, the generator 200 transitionsto a first constant power mode (PI). If the output voltage exceeds asecond voltage limit (V_(limit_2)), the generator 200 transitions to asecond constant power mode (P2). If the output voltage exceeds a thirdvoltage limit (V_(limit_3)), the generator 200 transitions to theconstant voltage mode, where the output voltage is limited and heldconstant. In an exemplary embodiment, the first voltage limit(V_(limit_1)), the second voltage limit (V_(limit_2)), and the thirdvoltage limit (V_(limit_3)) are set by a user or by the generator 200(e.g., from a look-up table).

Similarly, an exemplary controller 224 transitions from constant voltagemode to constant power mode and to constant current mode as inductorcurrent i_(L)(t) increases. Specifically, in an exemplary embodiment,the generator 200 operates in the constant voltage mode if the inductorcurrent does not exceed a first current limit (I_(limit_1)). If theinductor current does exceed the first current limit (I_(limit_1)), thenthe mode transitions to the second constant power level. If the inductorcurrent exceeds a second current limit (I_(limit_2)), then the modetransitions to the first constant power level. If the inductor currentexceeds a third current limit (I_(limit_3)), the generator 200transitions to the constant current mode, where the inductor current islimited and held constant. In an exemplary embodiment, the first currentlimit (I_(limit_1)), the second current limit (I_(limit_2)), and thethird current limit (I_(limit_3)) are set by a user or by the generator(e.g., from a look-up table).

As described above, in order to achieve the constant current, the DC-DCbuck converter 101 is controlled in current-program mode (CPM) and theDC-AC boost converter 102 is fixed at about 100% duty cycle d2. In orderto achieve constant power, in one embodiment the DC-DC buck converter101 may be controlled in non-linear carrier control (NLC) mode and theDC-AC boost converter 102 is fixed at about 100% duty cycle d2. Inanother embodiment, the DC-DC buck converter 101 is fixed at about 100%duty cycle d1 and the DC-AC boost converter 102 is controlled in CPM. Inorder to achieve constant voltage, the DC-DC buck converter 101 may befixed at 100% duty cycle d1 and the DC-AC boost converter 102 is fixedat a predetermined duty cycle d2, which may be less than 100%.

The generator 200 according to the present disclosure is capable ofoutputting energy for generating plasma having any user-settablefrequency, such that the waveforms have an infinitely variablefrequency, which may be adjusted without terminating energy generation.In embodiments, the frequency may be adjusted manually, e.g., by theuser, or automatically, e.g., by the generator 200, in response toenergy delivery feedback or any other suitable parameter, e.g., time, asdescribed in further detail below. Adjustments to the frequency may beaccomplished at the DC-AC boost converter 102. In particular, thecontroller 224 adjusts the duty cycle d2 of the control signals suppliedto the switching elements 102 a-102 d of the DC-AC boost converter 102.

In embodiments, the generator 200 may include discrete frequencysettings, which may be input via the user interface 241 and/or theinstrument 12. In further embodiments, the generator 200 may include aninput for continuously varying the frequency. The user interface 241 mayinclude a setting to adjust the crest factor. In further embodiments,the instrument 12 or other input devices (e.g., foot switch) may includeinputs to adjust the frequency. In additional embodiments, the frequencymay be adjusted by the controller 224 automatically based on changes inenergy, plasma, tissue properties (e.g., impedance), ionizable mediaflow rate, and combinations thereof. In particular, the generator 200may measure any suitable energy, plasma and/or tissue parameter usingthe sensors 280 including, but not limited to, voltage, current, phase,impedance, ionizable media flow rate, and combinations thereof andautomatically adjust the frequency in response to this measurement.

With reference once again to FIG. 1, the system 10 provides a flow ofplasma through the instrument 12 to a workpiece (e.g., tissue). Plasmafeedstocks, which include ionizable media and optional precursorfeedstocks, are supplied by the ionizable media source 16 to the plasmainstrument 12. The ionizable media source 16 may include various flowsensors and controllers (e.g., valves, mass flow controllers, etc.) tocontrol the flow of ionizable media to the instrument 12. The flow ratemay be adjusted to provide for laminar flow rate, turbulent flow rate,and any combinations thereof. During operation, the ionizable mediaand/or the precursor feedstock are provided to the plasma instrument 12where the plasma feedstocks are ignited to form plasma effluentcontaining ions, radicals, photons from the specific excited species andmetastables that carry internal energy to drive desired chemicalreactions in the workpiece or at the surface thereof. The feedstocks maybe mixed upstream from the ignition point or midstream thereof (e.g., atthe ignition point) of the plasma effluent.

The ionizable media source 16 may include a storage tank, a pump, and/orflow meter (not explicitly shown). The ionizable media may be a liquidor a gas such as argon, helium, neon, krypton, xenon, radon, carbondioxide, nitrogen, hydrogen, oxygen, etc. and their mixtures, and thelike. These and other gases may be initially in a liquid form that isgasified during application. The precursor feedstock may be either insolid, gaseous or liquid form and may be mixed with the ionizable mediain any state, such as solid, liquid (e.g., particulates or droplets),gas, and the combination thereof.

With continued reference to FIG. 1, the ionizable media source 16 may becoupled to the plasma instrument 12 via tubing 14. The tubing 14 may befed from multiple sources of ionizible media and/or precursorfeedstocks, which may combined into unified tubing to deliver a mixtureof the ionizable media and the precursor feedstock to the instrument 12at a proximal end thereof. This allows for the plasma feedstocks, e.g.,the precursor feedstock and the ionizable gas, to be delivered to theplasma instrument 12 simultaneously prior to ignition of the mixturetherein.

Ionizable media may be measured using a gas flow sensor (not shown)disposed within the instrument 12 or anywhere along the tubing 14 and/orat the ionizable media source 16. The gas flow sensor is coupled to thegenerator 200 and provides flow rate measurements to the generator 200for adjustment of the frequency in response to the flow ratemeasurement. In embodiments, the flow rate of ionizable media may bedetermined using impedance and other electrical properties at thegenerator 200 using the sensors 280.

In another embodiment, the ionizable media and precursor feedstocks maybe supplied at separate connections, such that the mixing of thefeedstocks occurs within the plasma instrument 12 upstream from theignition point such that the plasma feedstocks are mixed proximally ofthe ignition point.

In a further embodiment, the plasma feedstocks may be mixed midstream,e.g., at the ignition point or downstream of the plasma effluent,directly into the plasma. It is also envisioned that the ionizable mediamay be supplied to the instrument 12 proximally of the ignition point,while the precursor feedstocks are mixed therewith at the ignitionpoint. In a further illustrative embodiment, the ionizable media may beignited in an unmixed state and the precursors may be mixed directlyinto the ignited plasma. Prior to mixing, the plasma feedstocks may beignited individually. The plasma feedstock may be supplied at apredetermined pressure to create a flow of the medium through theinstrument 12, which aids in the reaction of the plasma feedstocks andproduces a plasma effluent. The plasma according to the presentdisclosure may be generated at or near atmospheric pressure under normalatmospheric conditions.

In one embodiment, the precursors may be any chemical species capable offorming reactive species such as ions, electrons, excited-state (e.g.,metastable) species, molecular fragments (e.g., radicals) and the like,when ignited by electrical energy from the generator 200 or whenundergoing collisions with particles (electrons, photons, or otherenergy-bearing species of limited and selective chemical reactivity)formed from ionizable media 16. More specifically, the precursors mayinclude various reactive functional groups, such as acyl halide,alcohol, aldehyde, alkane, alkene, amide, amine, butyl, carboxlic,cyanate, isocyanate, ester, ether, ethyl, halide, haloalkane, hydroxyl,ketone, methyl, nitrate, nitro, nitrile, nitrite, nitroso, peroxide,hydroperoxide, oxygen, hydrogen, nitrogen, and combination thereof. Inembodiments, the precursor feedstocks may be water, halogenoalkanes,such as dichloromethane, tricholoromethane, carbon tetrachloride,difluoromethane, trifluoromethane, carbon tetrafluoride, and the like;peroxides, such as hydrogen peroxide, acetone peroxide, benzoylperoxide, and the like; alcohols, such as methanol, ethanol,isopropanol, ethylene glycol, propylene glycol, alkalines such as sodiumhydroxide, potassium hydroxide, amines, alkyls, alkenes, and the like.Such precursor feedstocks may be applied in substantially pure, mixed,or soluble form.

With reference to FIGS. 1, 5, and 6, the instrument 12 includes a handlehousing 100 having a proximal end 102 and a distal end 104. The housing100 also includes a lumen 106 defined therein having a proximal endcoupled to the gas tubing 14 from the ionizable media source 16 and adistal end terminating at the distal end 104 of the housing 100. Theinstrument 12 also includes an elongated body 120 having a shaft housing122 defining a lumen 124 therethrough as shown in FIG. 6. The shafthousing 122 may be rigid or flexible. In particular, the lumens 106 and124 are in gaseous and/or fluid communication with the ionizable mediasource 16 allowing for the flow of ionizable media and precursorfeedstocks to flow through the lumens 106 and 124.

With reference to FIGS. 5 and 6, conductors 4 a, 4 b are coupled to theelectrodes 108 and 110 (FIG. 6), respectively. The conductors 4 a, 4 bextend through the housing 100 and shaft housing 122 of the elongatedbody 120 and are connected to the generator 200 via the cable 4. Thecable 4 may include a plug (not shown) connecting the instrument 12 tothe generator 200 at the connector 258. The conductor 4 a is coupled tothe proximal end of the electrode 108. The conductor 4 b may be a leador a wire embedded in the shaft housing 122 and is coupled to theelectrode 110 by exposing a distal portion of the conductor 4 b.

The shaft housing 122 may have a diameter from about 2 mm to about 20 mmallowing the instrument 12 to be inserted through operating ports of anendoscope or access ports in laparoscopic procedures as well as naturalbody orifices for application of the plasma effluent at the operatingsite during minimally invasive procedures.

The shaft housing 122 may be formed from any suitable dielectricmaterial including thermoplastics, such as acrylics, celluloid,cellulose acetate, cyclic olefin copolymer, ethylene-vinyl acetate,fluoropolymers (e.g., polytetrafluoroethylene), ionomers,polyoxymethylene, polyacrylates, polyacrylonitrile, polyamide,polyamide-imide, polyaryletherketon, polybutadiene, polybutylene,polybutylene terephthalate, polycaprolactone,polychlorotrifluoroethylene, polyethylene terephthalate,polycyclohexylene dimethylene terephthalate, polycarbonate,polyhydroxyalkanoates, polyketones, polyester, polyethylene,polyetheretherketone, polyetherketoneketone, polyetherimide,polyethersulfone, chlorinated polyethylene, polyimide, polylactic acid,polymethylpentene, polyphenylene oxide, polyphenylene sulfide,polyphthalamide, polypropylene, polystyrene, polysulfone,polytrimethylene terephthalate, polyurethane, polyvinyl acetate,polyvinyl chloride, polyvinylidene chloride, styrene-acrylonitrile, andcombinations thereof.

With reference to FIG. 6, the instrument 12 further includes anapplicator tip 130 coupled to the elongated body 120 at the distal endthereof. In embodiments, the applicator tip 130 is inserted into thedistal end of the lumen 124. The tip 130 may be formed from any suitabledielectric materials including the thermoplastic materials describedabove if the temperature of the plasma is sufficiently low or any othersuitable heat-resistant dielectric material, including ceramicmaterials. Suitable ceramic materials include, but are not limited to,metal oxide ceramics, non-oxide ceramics, ceramic composites, andcombinations thereof. Suitable oxide ceramics include zirconium oxide,aluminum oxide, silica oxide, magnesium oxide, iron oxide, calciumoxide, yttrinum oxide, cerium oxide, alumina oxide, silicon oxide,calcium silicate, copper oxide, nickel oxide, praseodymium oxide,titanium oxide, erbium oxide, europium oxide, holmium oxide, chromiumoxide, manganese oxide, vanadium oxide, cobalt oxide, neodymium oxideand combinations and composites thereof such as fiber composites, metaloxide composites, non-oxide composites, alumina/zirconia composites, andthe like.

The applicator tip 130 also includes a lumen 136 defined therethroughthat is fluid communication with the lumen 124. The lumen 136 may haveany suitable shape for tailoring the size and/or shape of the plasmaplume generated by the instrument 12. In embodiments, the lumen 124 mayalso include one or more surfaces for further shaping (e.g., narrowing)the plasma plume prior to exiting the instrument 12.

With reference to FIG. 6, the instrument 12 also includes two or moreelectrodes 108, 110 disposed within the applicator tip 130, shown asinner and outer electrodes, respectively. The electrodes 108 and 110 maybe formed from a conductive material including metals, such as stainlesssteel, copper, aluminium, tungsten, and combinations and alloys thereof.The electrodes 108 and 110 may have any suitable shape for conductingelectrical energy and igniting the ionizable media including, but notlimited to, rings, strips, needles, meshes, and the like. The electrodes108 and 110 may also be disposed outside or within the lumen 124 forcapacitive coupling with the ionizable media as described in furtherdetail below. The ionizable media in conjunction with the optionalprecursor feedstocks is ignited by application of energy through theelectrodes 108 and 110 to form a plasma plume exiting through an opening115 of the applicator tip 130.

In embodiments, the electrode 108 may be configured as an innerelectrode as shown in FIG. 6. The electrode 108 may be enclosed in aninsulative layer 108 a and may be supported within the lumen using aspacer 113. The electrode 110 is disposed on an outer surface 132 of theapplicator tip 130. The electrode 110 may include one or more electrodesthat are insulated from the electrode 108 by the dielectric material ofthe applicator tip 130 allowing for capacitive coupling between theelectrodes 108 and 110.

In further embodiments, the instrument 12 may include an identifier (notshown) that is configured to store one or more values corresponding toproperties of the instrument 12. The identifier may be RFID, EEPROM orany other suitable storage medium accessible by the generator 200.Values stored in the identifier may include, but are not limited to,electrode type/structure, dimensions of the applicator tip 130,shape/structure of the lumen 136, serial number, and the like. Infurther embodiments, the storage medium (e.g., non-transitory)identifier may be wholly or partially rewritable and may store usagedata including sterilization counts, usage counts, time used and thelike. The generator 200 may include a corresponding reader/writerconfigured to interface with the identifier 119. The generator 200 maytailor its output based on the data stored in the identifier as well asupdate the identifier to reflect usage/sterilization data after theinstrument 12 is used.

With reference to FIGS. 1 and 5, the instrument 12 also includes one ormore activation switches 150 a, 150 b, 150 c, each of which extendsthrough top-half shell portion of housing 100. Each activation switch150 a, 150 b, 150 c is operatively supported on a respective tactileelement (e.g., a snap-dome switch) provided on a switch plate 154. Eachactivation switch 150 a, 150 b, 150 c controls the transmission ofelectrical energy supplied from generator 200 to the electrodes 108 and110. The activation switches 150 a-150 c transmit control signals via avoltage divider network (VDN) or other circuit control means throughcontrol leads within the cable 4 to the generator 200. For the purposesherein, the term “voltage divider network” relates to any known form ofresistive, capacitive or inductive switch closure (or the like) whichdetermines the output voltage across a voltage source (e.g., one of twoimpedances) connected in series. A “voltage divider” as used hereinrelates to a number of resistors connected in series, which are providedwith taps at certain points to make available a fixed or variablefraction of the applied voltage.

With reference back to FIG. 1, the instrument 12 further includes avariable setting element, e.g., slide switch 158 slidingly supported onor within housing 100 in a guide channel 160 defined therein. The switch158 may be configured to function as a slide potentiometer, sliding overand along VDN. The switch 158 has a first position at a proximal-mostposition (e.g., closest to cable 4) corresponding to a lowest frequencysetting, a second position wherein the switch 158 is at a distal-mostposition corresponding to highest frequency setting. The switch 158 maybe disposed in a plurality of intermediate positions wherein the switch158 is at positions between the distal-most position and theproximal-most position corresponding to various intermediate frequencysettings. As can be appreciated, the frequency settings from theproximal end to the distal end may be reversed, e.g., high to low.Activation switches 150 a-150 c and the switch 158 are described infurther detail in a commonly-owned U.S. Pat. No. 7,879,033, the entirecontents of which are incorporated by reference herein.

Frequency may be controlled either through the generator 200 and/or theinstrument 12. With reference to FIG. 2, the screen 244 may be atouchscreen that allows for control of the outputs the connectors 256and 258 as well as the frequency of the generator 200. In embodiments,the screen 244 may be replaced and/or supplemented by other controls(e.g., keyboard, buttons, etc.). The screen 244 includes input buttonsfor adjusting the frequency. This may be accomplished by a variety ofcontrol schemes, shown on the screen 244 as graphical user interfaceelements, such as a variable setting element (e.g., slidable bar),predefined increment buttons, text and/or number inputs, andcombinations thereof. The frequency settings may be displayed as aslider of suitable frequency settings, discrete frequency input,numerical input, or any other input for setting frequency. The frequencysettings are used by the generator 200 to adjust the frequency asdescribed above to achieve a desired frequency of the excitation energyfor the plasma outputted by the instrument 12.

The instrument 12 may also control various properties of the plasmabeam. The activation switches 150 a-150 c may be used to activate thegenerator 200 and/or to control the flow of ionizable media from theionizable media source 16. The slide switch 158 is configured to adjustthe frequency as described above to achieve a desired degree offrequency of the plasma outputted by the instrument 12.

In embodiments, additional input devices may be used such as footswitches or handheld keyboards and/or remotes. The input devices (e.g.,activation switches 150 a-150 c) may be two-stage switches where uponactivation of the first stage, ionizable media and RF energy aresupplied to the instrument 12 at a sufficient level to prime the activeplasma field within the lumen 106 to initiate non-therapeuticionization. This enables the user to visualize the target tissuerelative to the non-therapeutic ionized gas plume. The generator 200 mayinclude a feedback control loop to ensure the pre-ionization level isachieved and maintained at minimum needed RF power. In embodiments, asingle wave spike may be generated to maintain sufficient ionized fieldwithout over heating the plasma instrument by minimizing RMS powerdelivered to pre-ionization field. In further embodiments, trace amountsof substantially non-electronegative compositions may be added toimprove visibility of the ionized gas. Suitable tracer compositionsinclude compounds such as sodium, neon, xenon, combinations thereof, andthe like. The closure of the second stage of the switch increases RFpower to therapeutic levels thereby initiating targeted therapeuticresults.

The present disclosure provides for a plasma electrosurgical system withvariable frequency, which allows for real-time adjustment of the plasmabeam, thereby allowing for achieving specific surgical effects. Thesystem allows for a single electrosurgical generator to be used forgenerating various plasma effects thereby reducing the cost of operatingroom equipment. In particular, combination of low and high-temperatureplasma in a single instrument improves the utility of both technologies,and may permit novel surgical techniques, such as surface sterilizationof tissue using cold plasma followed by dissection using hot plasma, ordissection using hot plasma followed by cold plasma drug delivery.

Although the illustrative embodiments of the present disclosure havebeen described herein with reference to the accompanying drawings, it isto be understood that the disclosure is not limited to those preciseembodiments, and that various other changes and modifications may beeffected therein by one skilled in the art without departing from thescope or spirit of the disclosure. In particular, as discussed abovethis allows for tailoring of the relative populations of plasma speciesto meet needs for the specific process desired on the workpiece surfaceor in the volume of the reactive plasma.

What is claimed is:
 1. A plasma system comprising: a plasma instrument;an ionizable media source in fluid communication with the plasmainstrument and configured to supply ionizable media thereto; and avariable frequency energy source coupled to the plasma instrument andconfigured to: supply an excitation waveform including a plurality ofcycles to the plasma instrument sufficient to ignite the ionizable mediasupplied by the ionizable media source to generate a plasma effluent;and adjust a frequency of the excitation waveform on a cycle-by-cyclebasis to a first frequency at which the plasma effluent is at a firsttemperature for non-thermal treatment of tissue and a second frequency,higher than the first frequency, at which the plasma effluent is at asecond temperature, higher than the first temperature, for thermaltreatment of tissue.
 2. The plasma system according to claim 1, whereinthe ionizable media source is adapted to be coupled to the variablefrequency energy source.
 3. The plasma system according to claim 2,wherein the variable frequency energy source is configured to adjust thefrequency based on a flow rate of the ionizable media from the ionizablemedia source.
 4. The plasma system according to claim 1, wherein theplasma instrument includes: an elongated body defining a lumentherethrough; a first electrode and a second electrode; and a slideswitch for varying a frequency of supplied energy.
 5. The plasma systemaccording to claim 4, wherein the plasma instrument includes anapplicator tip coupled to a distal end of the elongated body.
 6. Theplasma system according to claim 5, wherein the applicator tip defines asecond lumen in fluid communication with the lumen of the elongatedbody.
 7. The plasma system according to claim 6, wherein the firstelectrode is disposed on an outer surface of the applicator tip.
 8. Theplasma system according to claim 7, wherein the second electrode isdisposed within at least one of the lumen of the elongated body or thesecond lumen.
 9. The plasma system according to claim 1, wherein thevariable frequency energy source includes: a non-resonant radiofrequency output stage configured to output the excitation waveform; anda controller coupled to the non-resonant radio frequency output stage,the controller configured to adjust the frequency of the excitationwaveform on a cycle-by-cycle basis.
 10. The plasma system according toclaim 9, wherein the non-resonant radio frequency output stage includes:a DC-DC buck converter configured to output a DC waveform, the DC-DCbuck converter including at least one first switching element operatedat a first duty cycle.
 11. The plasma system according to claim 10,wherein the non-resonant radio frequency output stage further includes:a DC-AC boost converter coupled to the DC-DC buck converter andincluding at least one second switching element operated at a secondduty cycle, the DC-AC boost converter configured to convert the DCwaveform to generate the excitation waveform.
 12. The plasma systemaccording to claim 11, wherein the controller is coupled to the DC-DCbuck converter and the DC-AC boost converter and the controller isfurther configured to adjust the second duty cycle of the excitationwaveform.
 13. A method comprising: supplying ionizable media from anionizable media source to a plasma instrument; supplying an excitationwaveform including a plurality of cycles from a variable frequencyenergy source to the plasma instrument to ignite the ionizable mediasupplied by the ionizable media source and to generate a plasma effluentat a first frequency at which the plasma effluent is at a firsttemperature for non-thermal treatment of tissue or at a second frequencyhigher than the first frequency at which the plasma effluent is at asecond temperature higher than the first temperature for thermaltreatment of tissue; and adjusting a frequency of the excitationwaveform between the first frequency of the excitation waveform and thesecond frequency of the excitation waveform on a cycle-by-cycle basis.14. The method according to claim 13, wherein adjusting of the frequencyincludes inputting a desired frequency using a frequency user interfaceof the variable frequency energy source.
 15. The method according toclaim 13, wherein adjusting of the frequency includes inputting thefrequency based on a flow rate of the ionizable media from the ionizablemedia source.
 16. The method according to claim 13, wherein supplyingthe excitation waveform includes operating at least one switchingelement of a DC-AC boost converter at a duty cycle to convert a DCwaveform to generate the excitation waveform.
 17. The method accordingto claim 16, wherein adjusting of the frequency includes adjusting theduty cycle.